In the art of mechanically harvesting crops, it is known that self-propelled agricultural vehicles, such as combine harvesters and forage harvesters, are used to mechanically harvest crops. Typically, these vehicles are equipped with a harvesting implement, or header, that can, for instance, include a reel or other apparatus for pulling crops into an array of blades for cutting the crops, wherein the cut crop material is pulled or otherwise conveyed farther into the header by an auger or other apparatus. Once past the auger, the cut crop material is carried by an elevator or feederhouse to a threshing and sorting mechanism or system that removes unwanted chaff material from the desired crop matter before the crop matter reaches a storage compartment or tank carried by the vehicle.
However, this simple crop harvesting process is complicated by the fact that stones and other discrete hard objects are often pulled into the header with the crops. In the context of this disclosure, the terms “stones,” “rocks,” “objects,” and “hard materials” are used interchangeably and define equivalent matter to include any discrete undesirable matter such as stones, rocks, pieces of metal, and pieces of wood, that is separable from the cut crop material (i.e., harvested crop plant material) and thus considered to be foreign to the crops. Unfortunately, stones and other hard debris can cause expensive damage to the elevator and threshing mechanisms; therefore, various methods and apparatuses have been developed to detect and remove stones and other potentially damaging foreign objects from the header before the cut crop material is carried by the elevator into the threshing and sorting mechanism.
Typically, the stone detection methods and apparatuses of the prior art include a stone detection circuit that operates a mechanism for removing any stones or hard objects. For example, U.S. Pat. No. 3,675,660 to Girodat, which is incorporated herein by reference in its entirety, discloses a rock detection circuit that includes a rock detector, a bandpass filter, a peak signal detector, an amplifier, and a solenoid operated trap door placed along the cut crop path before the crop elevator. The rock detector is a piezoelectric ceramic disc that picks up vibrations as the crop material passes and sends a sensing signal to the bandpass filter. Rocks of a certain size are known to generate higher frequency vibrations than the crop material, so the bandpass filter removes low frequency signals from the sensing signal before sending the filtered signal to the peak signal detector.
Extremely large stones entering the combine feeder housing sometimes are not detected by the system of the Girodat patent. Several mechanisms are responsible for this. First, the physical size of a very large stone and the feeder front roll configuration prevents the required direct impact of the stone on the existing flat sensor plate. Instead, the stone is pinched between the front roll and the sensor plate which results in the stone being scraped and dragged across the plate. Second, when a very large stone does impact the sensor plate, acoustical signatures below about 2 kHz are generated—well below the ASP (Advanced Stone Protection) electronic box bandpass filter center frequency of 5 kHz. Only a small amount of signal is generated within the pass band of the filter. Thus, a very large stone is often not sensed and is thrust into the combine resulting in damage.
Thus, the peak signal detector generates a signal only if the filtered signal has an amplitude greater than a predetermined amplitude (“threshold amplitude”), thereby filtering out background noise signals. When the filtered signal exceeds the predetermined amplitude, the peak signal detector generates a signal that is amplified by an amplifier, which sends an activating signal to a solenoid, which operates to open the trap door so that the hard foreign object will fall out of the header. Unfortunately, there is a lot of background noise due to vibrations generated by the vehicle's engine, jarring of the vehicle as it travels along the ground, and rock impacts on the exterior of the header during harvesting operations.
Consequently, unless sensitivity of the rock detection circuit is precisely set, either the trap door will open unnecessarily thereby spilling valuable crop on the ground or the trap door will not open when needed so that many large stones will reach the elevator and threshing mechanism resulting in damage to the vehicle. It is noted that Girodat's rock detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filter, or the threshold amplitude of the peak signal detector.
In an attempt to mitigate the effect of background vibrations, U.S. Pat. No. 4,275,546 to Bohman et al. discloses a stone discriminator circuit that uses a pair of piezoelectric crystals that are vibrationally isolated from the header and the harvester by two vibration isolators. The two piezoelectric crystals are set to detect different vibration frequencies, one crystal detects vibration generated by the crop material and the other crystal detects vibration generated by stones. Each crystal sends signals to its respective bandpass filter, then to a difference amplifier that receives input from both bandpass filters. The difference amplifier detects the difference between the signals from the two crystals and outputs an amplified signal to a threshold circuit.
The threshold circuit generates a signal to operate a trap door or an alarm only if the amplified signal from the difference signal exceeds a threshold amplitude. In other words, the two crystals provide comparative information with respect to the background vibrations and superimposed rock vibrations in an attempt to weed out the background events from stone impact events near the crystals. However, Bohman's circuit also has the drawback that the stone discriminator circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.
U.S. Pat. No. 4,720,962 to Klinner discloses a means for detecting stones and metal, which is a circuit including a vibration detector and a metal detector for detecting unwanted objects in a forage harvester. The vibration detecting portion of the circuit includes a vibration sensor, a high pass filter and a comparator, so that a vibration detecting signal is generated that is frequency filtered and that represents an event exceeding a minimum threshold amplitude. Input from a metal sensor and input from the vibration detecting portion feed into the remaining portion of the stone and metal detection circuit to activate a door system to get rid of the unwanted object. It is noted that the stone and metal detection circuit includes a timing circuit so that the door system stays open for only a predetermined period of time. However, Klinner's stone and metal detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.
Some other known stone detection or protection systems include two sensor plates and related two electronic bandpass filters in the stone detection or protection module employed to process signals from each plate in order to produce stone trap door openings whenever a stone impacts one of the plates. Each of these two filters passes a range of frequencies centered about a certain frequency. For the upper plate the center frequency is 3.1 kHz and for the lower plate the center frequency is 5 kHz.
Controlled tests strongly suggest that the upper sensor plate is relatively ineffective in contributing to stone detection or protection. Lab testing has conclusively shown that very large stones generate impact signals in the lower frequency region below about 2 kHz. Only a small amount of signal from the very large stones is available in the 5 kHz filter pass band. Medium to small stones generate impact signals mainly in the region above 2 kHz.
It has also been discovered that high force impacts of the largest stones (or even hard ear corn) produces a very large low spectrum electrical signal that can sometimes overload the electronic circuitry of the 5 kHz filter in the ASP module. Whenever an overload occurs, the amount of signal available in the 5 kHz region is reduced. This will adversely affect detection performance.
Therefore, the present invention endeavors to provide an improved method for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester, and an apparatus for performing this method that reliably produces cut crop material that is essentially solely cut crop matter that is an improvement over the prior art devices and methods.
Accordingly, a primary object of the present invention is to overcome the disadvantages of the prior art methods and apparatuses for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that achieves adequate detection rates for the hard foreign objects, so that the objects can be reliably removed.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for external adjustment of various detection parameters by an operator to achieve the improved detection rates for the hard foreign objects.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for the system to internally adjust to various internal and/or external influences that are transparent to the operator to achieve the improved detection rates for the hard foreign objects.